Insulin Resistance and Cancer: The Metabolic Connection You Need to Understand

I ate my way into Type 2 Diabetes. Then I ate my way into Prostate Cancer. Those are harsh statements, and of course, it's always more complicated than that - but there is so much truth in them that I can state them and own them. Type 2 Diabetes is a metabolic disease, and over 90% of all cancers are metabolic in origin. As I related in earlier posts, I gradually progressed through pre-diabetes to full-blown diabetes before I learned that I could reverse it. Learning and doing are two different things, of course, which is always the problem in the human condition. Even after I had begun the reversal, I wasn't truly involved in a completely healthy regimen. So the cancer occurred. It could have been for any number of reasons, but mainly because of what I know now - that the metabolic "terrain" for cancer is a continuation of the same terrain for diabetes and other chronic diseases.

The Connection I Missed - Even as a Doctor

Even as a physician, I didn't think deeply about the fact that diabetes and cancer can be connected by the same biology. I believed - naively - that diabetes is about blood sugar and cancer is about genes and genetic bad luck (which in some cases it is). What I didn't understand was that long before blood sugar climbs too far past normal, the body can develop an excess of insulin - the hormone produced by the pancreas that pushes glucose into cells.

When you eat sugar or other carbohydrates, more insulin is produced. If you continue that pattern of eating, so much insulin is produced that your cells become resistant to it. Insulin levels increase and stay high, and sugar gets deposited in other organs, leading to fatty liver and so-called "visceral fat" - that stubborn belly fat many people struggle with.

But insulin isn't just for handling sugar. It is a powerful growth signal. When I say I "ate my way" into these illnesses, I'm not talking about one meal or one holiday - I'm talking about years of repeated, insulin-spiking choices: fast food, ultra-processed foods, snack foods, and the like. I could easily justify those choices because I was busy, tired, or stressed. The result was that I became insulin resistant: my cells stopped responding normally, and my pancreas had to produce more and more insulin just to keep my blood sugar "relatively" normal.

And I'm not alone. Over 100 million adults in the United States are diagnosed with Type 2 diabetes or pre-diabetes. At least 8 million adolescents under age 20 have pre-diabetes. As a nation, we are a metabolic mess.

What Insulin Actually Is - Beyond Sugar

In addition to its effect on blood sugar, insulin is one of the body's strongest signals for growth and storage. In the short term, that's useful - it moves nutrients into cells and supports repair. The problem is chronic elevation.

With insulin resistance, caused by chronically elevated insulin levels, the cells don't respond the same way. The pancreas compensates by increasing insulin output to the point where insulin in the blood remains elevated and, over time, simply doesn't diminish. Blood sugar may look only mildly abnormal for years, but the insulin level can be high long before a person is diagnosed with "pre-diabetes." In other words, the body can be broadcasting this powerful growth-and-storage signal continuously, even before someone is officially diabetic.

How Excess Insulin Impacts Cancer Risk

Many cancers occur because of what are called "epigenetic changes" - changes around the DNA that lead to a cancer cell forming. This can happen because of a fault in DNA during cell division, or because of harmful changes in the cellular environment that trigger cancer development. All of these factors, combined with chronically elevated insulin, matter - because cancers don't just grow randomly. They respond to signals.

Insulin, along with a related growth factor called IGF-1 (Insulin-like Growth Factor 1), can encourage cancer cell growth through three critical pathways:

1. Increased cell proliferation: More cell division means more opportunities for cancerous changes to take hold.
2. Inhibited apoptosis: Apoptosis is programmed cell death - the body's way of eliminating damaged cells. When this process is suppressed, cancer cells can become effectively immortal. Helping cancer cells "remember how to die" is a key principle in oncology.
3. Enhanced angiogenesis: The creation of new blood vessels that allow tumors to grow faster and larger.

IGF-1 is, in most circumstances, important for maintaining overall health. However, when insulin and IGF-1 are chronically elevated over prolonged periods, these growth-promoting effects can create an environment where early, undetectable cancers are more likely to thrive.

The Inflammation Connection

Excess insulin also leads to increased inflammation. Inflammation - which is distinct from infection - changes the environment around cells, making it easier for problems to persist and harder for the body to maintain its normal checks and balances. Chronic inflammation is a driver of many diseases, and its role in cancer development is increasingly well-documented.

What the Research Shows

The association between insulin resistance and many cancers is now well established in the scientific literature. Many cancer patients are measurably insulin resistant. Insulin resistance is associated with worse outcomes - higher recurrence rates and lower survival. Importantly, a person can exhibit insulin resistance without technically being diabetic.

The fact that this aspect of physiology is not routinely discussed with cancer patients is not the fault of any particular physician - it's part of the medical system as a whole. This point may seem small in the larger landscape of a cancer diagnosis and treatment, but the way I encourage people to look at it is this: if there is something relatively straightforward that someone can work on to increase their survival - even just a chance to do so - then why not do it?

I firmly believe cancer patients must be given every opportunity possible to increase their knowledge of their disease process and to engage in their own care.

Three Concrete Steps to Fight Insulin Resistance

1. Reduce Foods That Spike Insulin

Decrease sugar intake as close to zero as possible. Eat fewer refined carbohydrates - bread, pasta, rice. Reduce ultra-processed foods, which can be broadly defined as just about anything contained within a box or a bag. All of these foods rapidly increase blood sugar and therefore insulin production.

2. Consider Fasting (With Physician Guidance)

The longer you go without food, the less sugar circulates in your blood, the less stimulus there is for insulin release, and over time, insulin resistance diminishes. If you eat dinner at six and don't eat again until 7 AM, that's a 13-hour fast. If you can make it to lunch without food, that can extend to 17–19 hours. The longer the fast, the more you fight insulin resistance and the more you help your body fight back against cancer. Fasting is a powerful tool that deserves its own dedicated discussion, but for now, learn how to use it as part of your arsenal - always in conjunction with your physician's involvement.

3. Move. Consistently. Daily.

Exercise is one of the most effective insulin-sensitizing interventions available. Walking is outstanding exercise - walking with purpose, building speed and distance. Aim for 150–180 minutes per week or more. Walking after meals, adding resistance training (weight lifting), cycling, swimming - any regular exercise helps your muscles use sugar more effectively and reduces the need for your body to produce excess insulin.

A Personal Note

I'm not suggesting that managing insulin resistance is a cure for cancer. But I can tell you that as I learned this information while dealing with my own cancer - information that no one shared with me at the time, that I had to find on my own - it became one of the things that has allowed me to be healthier than I have been in 30 years. It has been part of the regimen that has helped me stay free of recurrence of a cancer that wants to recur.

If you have cancer, or know someone who does, please use this information. Everything we can do to help our bodies decrease the chance of getting cancer, or to fight it if there's a diagnosis, is worth pursuing. Ask questions. Do your own research. And ask more questions.

References

1. Cosmin Stan M, Paul D. Diabetes and Cancer: A Twisted Bond. Oncol Rev. 2024 May 21;18:1354549.
2. Màrmol JM, et al. Insulin resistance in patients with cancer: a systematic review and meta-analysis. Acta Oncol. 2023 Apr;62(4):364-371.
3. Chiefari E, et al. Insulin Resistance and Cancer: In Search for a Causal Link. Int J Mol Sci. 2021 Oct 15;22(20):11137.
4. Mirzaeva M, et al. Association of Obesity with Premenopausal Breast Cancer: Analyzing Molecular Subtypes. Archives of Breast Cancer. 2025;12(4).
5. Arcidiacono B, et al. Insulin resistance and cancer risk: an overview of the pathogenetic mechanisms. Exp Diabetes Res. 2012;2012:789174.